A biological treatment method and apparatus for oily sludge

Abstract

This invention discloses a biological treatment method and apparatus for oily sludge, relating to the field of oil and gas field development. It is achieved through the following steps: Hot water A is added to oily sludge A, and the mixture is stirred to facilitate sludge flow and remove impurities and large-particle sand from the sludge; the resulting oil-sludge-water mixture is added to flotation water B, stirred, and then the surface crude oil components are collected using a flotation device. This process is repeated 12-18 times, and the wastewater is discharged, with sludge slurry B reserved for later use; sludge slurry B is then injected into flotation water C, heated, and saturated with aeration. Flotation is performed every 8-12 hours, collecting the upper layer of crude oil components, discharging the middle wastewater, and leaving sludge C at the bottom; the oily sludge treatment is completed in 5-7 days. The composite biological agent system used in this invention is non-toxic, non-corrosive, biodegradable, and does not produce secondary pollution, making it environmentally friendly. Its treatment conditions are mild, do not involve high temperature or high pressure, are safer, and have a shorter treatment cycle and higher efficiency.

Description

Technical Field

[0001] This invention relates to an oily sludge treatment process and its supporting treatment equipment in the fields of oil and gas field development and oilfield resources and environment technology, and in particular to a deep treatment method and dedicated equipment for oily sludge. Background Technology

[0002] Oilfield development and production processes generate large amounts of oily sludge, which is listed as "hazardous waste" in the national hazardous waste list. Improper disposal can not only harm the natural environment and surrounding residents, but also result in penalties from environmental protection departments and even legal sanctions. With the increasing intensity of environmental penalties and supervision in recent years, oilfields are increasingly dissatisfied with simply treating oily sludge to an oil content of less than 2%; they are constantly seeking higher standards of deep treatment for oily sludge, such as oil content of less than 3‰ or even lower.

[0003] Currently, the commonly used "thermochemical cleaning technology" can only achieve a petroleum content of ≤2% after oily sludge treatment. To meet the standard requirement of ≤3‰ petroleum content, advanced oily sludge treatment technology is needed. Among existing advanced treatment technologies, incineration technology, due to the risk of dioxin production from high-temperature aerobic combustion and the cumbersome process of flue gas treatment, has gradually become an unselected technology. Pyrolysis technology is limited by high treatment costs, low processing loads, and imperfect equipment and processes. Chemical technology using oxidants has disadvantages such as high dosage, high treatment costs, and the potential for secondary pollution. Microbial technology is a green and environmentally friendly technology, but traditional microbial technologies are limited by large footprints, low efficiency (treatment cycles ranging from one month to half a year), and susceptibility to environmental factors such as temperature. For example, the leading North American petroleum biodegradation technology Oil Gator (preferred by the US EPA) has an in-situ remediation treatment cycle of 90-180 days, while the microbial sludge treatment technology used by the Changqing Oilfield Design Institute in China requires a batch treatment cycle of 30-40 days when the TPH (Total Petroleum Hydrogenation) target is 2%. Summary of the Invention

[0004] This invention aims to overcome the shortcomings of existing technologies and provides a biological treatment method and apparatus for oily sludge. The invention uses a "high-efficiency biological agent system" as its core, coupled with a high-efficiency treatment device, and precise control of environmental and operational conditions, achieving efficient and in-depth treatment of oily sludge.

[0005] The present invention provides a biological treatment method for oily sludge, which is achieved through the following steps:

[0006] (1) Fluidization and screening of oily sludge: Add hot water A at 50-75℃ to oily sludge A, stir to make the sludge easy to flow, and remove plastic products and sand with a particle size greater than 3mm from the oily sludge;

[0007] (2) Hot washing of oily sludge: Add 50-75°C air flotation water B to the oily sludge-water mixture obtained in step (1), and the weight ratio of oily sludge A: (hot water A + air flotation water B) is 1: (2-5). Stir at a speed of 60-120 r / min for 1-5 minutes, let stand for 10-15 minutes, and then collect the surface crude oil components through an air flotation device. Repeat the above process 12-18 times every 20-30 minutes, and discharge the sewage to the sewage collection tank and sludge slurry B for later use.

[0008] (3) Biological treatment of oily sludge: The sludge slurry B after hot washing in step (2) is injected into the flotation water C. The weight ratio of sludge slurry B to the injected flotation water C is 1: (1~5). The sludge slurry B is heated and the temperature is maintained at 36~40℃. The pH is adjusted to 6~11. The stirring speed is controlled at 120~220r / min. Saturated aeration is performed. Flotation is performed once every 8~12 hours. The upper crude oil components are collected through the oil collection device, the middle sewage is discharged to the sewage collection tank, and the bottom is sludge C. After 5-7 days, the petroleum content in sludge C drops to below 0.3%, and the treatment of oily sludge is completed.

[0009] The air-flotated water C is dissolved air water containing microbial fermentation broth, and the effective component of the microbial fermentation broth in the dissolved air water is 0.1-10% by weight.

[0010] As a further improvement of the present invention, the microbial fermentation agent in step (3) is *Rhodococcus faecalis* (Fan Qingsheng's Rhodococcus rubrum). Rhodococcus_qingshengii ), Microbacterium foliata ( Leaf microbacterium ), Pseudomonas putida ( Pseudomonas putida ), Microbacterium schrenckii ( Microbacterium schleiferi) and Dietzia (Dietzia) Highly efficient petroleum-degrading bacteria are constructed according to the volume ratio of (1-10): (1-10): (1-10)(1-10): (1-10).

[0011] As a further improvement of the present invention, waste hydrochloric acid or calcium oxide is added in step (3) to adjust the pH value.

[0012] As a further improvement of the present invention, the injection pressure of the air flotation water in steps (2) and (3) is 0.2 to 0.4 MPa.

[0013] This invention discloses a biological treatment device for oily sludge, comprising a biological tank. The biological tank includes an outer tank body and a support frame I. The bottom of the outer tank body has a through hole. An inner tank body is placed inside the outer tank body and its bottom is fixed to the through hole. A sludge discharge pipe C is provided at the bottom of the inner tank body. An annular cavity I is formed between the outer wall of the inner tank body and the inner wall of the outer tank body. An annular support plate is fixed between the upper end of the outer wall of the inner tank body and the inner wall of the outer tank body to seal the annular cavity I. An overflow pipe I for crude oil component C is provided on the upper part of one side of the outer tank body above the annular support plate. A sludge slurry B inlet pipe is provided above the overflow pipe I. An air blowing pipe I and a central wastewater C overflow pipe communicating with the inner tank body are provided on the upper part of the other side of the outer tank body. II. The lower part is provided with an vent pipe I that communicates with the inner tank; the air inlet of the air blowing pipe I is connected to the air tank II pipeline, and the air outlet passes through the outer tank and is placed at the upper edge of the inner tank; the upper end of the outer tank is provided with a sealing cover I, and a stirring device is provided at the center of the upper end of the sealing cover I; one or more semi-circular annular pipes are fixed around the outer side of the support frame I, and each of the semi-circular annular pipes is connected to the liquid inlet pipe of the dissolved air flotation water C. The other end of the liquid inlet pipe is connected to the water outlet pipe of the dissolved air tank II. One or more liquid outlet pipes of the dissolved air flotation water C are evenly fixed along the circumference of the outer wall of the semi-circular annular pipes. The other end of the liquid outlet pipe passes through the outer tank and the inner tank and is fixedly connected to the outer wall of the circular dissolved air water release pipe I fixed at the bottom of the inner tank.

[0014] As a further improvement of the present invention, the upper part of one side of the outer wall of the outer tank is provided with a circulating water inlet pipe connected to the annular cavity I, and the lower part of the other side is provided with a circulating water outlet pipe connected to the annular cavity I. The circulating water inlet pipe I and the circulating water outlet pipe I are respectively connected to the boiler III pipeline.

[0015] As a further improvement of the present invention, the upper end face of the annular dissolved air water release pipe I is evenly distributed with one or more sets of liquid outlet holes along its circumference, and the angle between two adjacent sets of liquid outlet holes is 45°.

[0016] As a further improvement of the present invention, the overflow pipe II is located below the annular support plate.

[0017] This invention discloses a biological treatment method for oily sludge, innovatively developing the synergistic application of multiple biotechnologies such as biological washing of oily sludge, deep biological degradation of residual oil, and microbial flocculation. This achieves high-standard treatment of oily sludge (petroleum hydrocarbons ≤3‰), while simultaneously realizing safe, green, and clean treatment of the sludge, which can be used for greening and reclamation. This invention incorporates a co-metabolic degradation technology using microbially secreted biosurfactants, decomposing enzymes, and highly efficient bacterial strains. In the initial stage, biosurfactants reduce interfacial tension to promote the biological desorption of oil and sludge, while decomposing enzymes reduce viscosity and thicken, accelerating the rapid desorption of petroleum hydrocarbons. In the later stage, under the controlled microbial metabolic conditions in a sludge reactor, the remaining petroleum hydrocarbons are deeply degraded through co-metabolic degradation by highly efficient bacterial strains. The pressurized dissolved air flotation technology utilizes increased pressure to significantly increase the dissolved oxygen content in the water. Then, by adjusting the water volume and flow rate through the dissolved air release port, dissolved oxygen is rapidly released, forming microbubbles that carry emulsified oil to the liquid surface for easy removal.

[0018] Compared with existing technologies, the present invention has the following advantages:

[0019] Compared with commonly used thermochemical cleaning technologies, the composite biological agent system used in this invention is non-toxic, non-corrosive, biodegradable, and does not produce secondary pollution, making it greener and more environmentally friendly. Compared with pyrolysis and incineration technologies, this invention offers milder treatment conditions, does not involve high temperature and high pressure, and is safer. Compared with traditional microbial treatment technologies, this invention has a shorter treatment cycle and is more efficient. Attached Figure Description

[0020] Figure 1~3 This is a schematic diagram of the structure of a biological treatment device for oily sludge according to the present invention;

[0021] Figure 4 This is a cross-sectional view of a circular dissolved air water release pipe. Implementation

[0022] Example 1

[0023] The present invention provides a biological treatment method for oily sludge, which is achieved through the following steps:

[0024] (1) Fluidization and screening of oily sludge: Add hot water A at 65°C to oily sludge A, stir to make the sludge easy to flow, and remove plastic products and sand with a particle size greater than 3mm from the oily sludge;

[0025] (2) Hot washing of oily sludge: Add 65°C air flotation water B to the oily sludge-water mixture obtained in step (1), and the weight ratio of oily sludge A to (hot water A + air flotation water B) is 1:3. Stir at 70 r / min for 1 to 5 minutes, let stand for 10 to 15 minutes, and then collect the surface crude oil components through the air flotation device. Repeat the above process 18 times every 20 to 30 minutes, and discharge the sewage to the sewage collection tank and sludge slurry B for later use.

[0026] (3) Biological treatment of oily sludge: The sludge slurry B after hot washing in step (2) is injected into the flotation water C. The weight ratio of sludge slurry B to the injected flotation water C is 1:5. The sludge slurry B is heated and the temperature is maintained at 36-40℃. The pH is adjusted to 6-11. The stirring speed is controlled at 130r / min. Saturated aeration is performed. Flotation demulsification is performed once every 8-12 hours. The upper crude oil components are collected through the flotation device, the middle sewage is discharged to the sewage collection tank, and the bottom is sludge C. After a total of 7 days of treatment, the concentration of petroleum in sludge C is reduced to below 0.3%.

[0027] The air-flotated water C is dissolved air water containing microbial fermentation broth, and the effective component of the microbial fermentation broth in the dissolved air water is 5% (by weight). The microbial fermentation agent contains *Rhodococcus flavonoids* (Fan Qingsheng). Rhodococcus_ qingshengii ), leaf microbacteria ( Leaf microbacterium ), Pseudomonas putida ( Pseudomonas stinky ), Microbacterium schrenckii ( Microbacterium schleiferi) It is a highly efficient petroleum-degrading bacterium composed of Dietzia in a volume ratio of 2:2:2:2:2.

[0028] Example 2

[0029] The present invention provides a biological treatment method for oily sludge, which is achieved through the following steps:

[0030] (1) Fluidization and screening of oily sludge: Add hot water A at 70°C to oily sludge A, stir to make the sludge easy to flow, and remove plastic products and sand with a particle size greater than 3mm from the oily sludge;

[0031] (2) Hot washing of oily sludge: The oily sludge-water mixture obtained in step (1) is put into a hot washing tank for hot washing. Then, air flotation water B with a temperature of 70℃ and a pressure of 0.2-0.4 MPa is added. The weight ratio of oily sludge A to (hot water A + air flotation water B) is 1:3. Then, the mixture is stirred at a speed of 60 r / min for 1-5 minutes. After stirring, it is left to stand for 12 minutes. Then, the surface crude oil components are collected through an air flotation device. The above process is repeated 18 times every 25 minutes. The wastewater is discharged to the wastewater collection tank and the sludge slurry B is left for use.

[0032] (3) Biological treatment: The sludge B after the hot washing treatment in step (2) is put into the biological tank, and the air flotation water C with a pressure of 0.2-0.4 MPa is injected. The weight ratio of sludge B to the injected air flotation water C is 1:3. The sludge B is heated and the temperature is maintained at 36-40℃. Waste hydrochloric acid or calcium oxide is added to adjust the pH to 7-9. The stirring speed is controlled at 180 r / min. Saturated aeration is performed. Air flotation demulsification is performed once every 10 hours. The upper crude oil components are collected through the air flotation device, the middle sewage is discharged to the sewage collection tank, and the bottom is sludge C. After 5 days of cumulative treatment, the concentration of petroleum in sludge C is reduced to below 0.3%.

[0033] The air-flotated water C is dissolved air water containing microbial fermentation broth, wherein the effective component of the microbial fermentation broth in the dissolved air water is 1-4%, and the microbial fermentation agent contains *Rhodococcus flavonoides* (Fan Qingsheng). Rhodococcus_qingshengii ), leaf microbacteria ( Leaf microbacterium ), Pseudomonas putida ( Pseudomonas putida ), Microbacterium schrenckii ( Microbacterium schleiferi) It is a highly efficient petroleum-degrading bacterium composed of Dietzia in a volume ratio of 3:3:3:3:3.

[0034] Example 3

[0035] In step (3) of the above embodiments 1 and 2, the biological treatment requires the use of a dedicated biological tank, such as... Figure 1~4 As shown, the biological tank includes an outer tank 1 and a support frame I2. The bottom of the outer tank 1 is provided with a through hole. The inner tank 3 is placed inside the outer tank 1 and its bottom is fixed to the through hole. A sludge discharge pipe 4 for mud C is provided at the bottom of the inner tank 3. An annular cavity I5 is formed between the outer wall of the inner tank 3 and the inner wall of the outer tank 1. An annular support plate 6 is fixed between the upper end of the outer wall of the inner tank 3 and the inner wall of the outer tank 1 to seal the annular cavity I5. A circulating water inlet pipe 19 connected to the annular cavity I5 is provided on the upper part of one side of the outer wall of the outer tank 1, and a circulating water outlet pipe 20 connected to the annular cavity I70 is provided on the lower part of the other side. The circulating water inlet pipe I19 and the circulating water outlet pipe I20 are respectively connected to the boiler III pipeline to maintain the temperature at 36-40℃ during the biological treatment process. A level gauge 24 is provided on one side of the outer wall of the outer tank 1, and the upper and lower ends of the level gauge 24 pass through the outer tank 1 and are connected to the inner tank 3, which allows the staff to observe the liquid level in the inner tank 3 at any time.

[0036] An overflow pipe I8 for crude oil component C is provided on the upper part of one side of the outer wall of the outer tank 1 above the annular support plate 6. Above the overflow pipe I8 is a feed pipe 9 for sludge slurry B. On the upper part of the other side of the outer wall of the outer tank 1, there is an air blowing pipe I10 and an overflow pipe II11 for sewage C in the middle, which is connected to the inner tank 3. At the lower part, there is a drain pipe I12 connected to the inner tank 3. The overflow pipe II11 is located below the annular support plate 6. The overflow pipe I8, overflow pipe II11 and drain pipe I12 are all connected to the waste liquid treatment tank. The air inlet of the air blowing pipe I10 is connected to the air tank II pipeline, and the air outlet passes through the outer tank 1 and is placed at the upper edge of the inner tank 3. The annular support plate 6 is inclined from the air blowing pipe I10 to the overflow pipe I8, so that the blown oil and foam can be better overflowed from the overflow pipe I8.

[0037] The outer tank 1 is provided with a sealing cover I13 at the upper end, and a stirring device is provided at the center of the upper end of the sealing cover I13. The stirring device includes a stirring motor 21, a stirring shaft 22 and a stirring paddle 23. The stirring motor 21 is fixed at the center of the upper end of the sealing cover 13. The output end of the stirring motor 21 passes through the sealing cover 13 and is fixedly connected to the upper end of the stirring shaft 22. Multiple stirring paddles 23 are evenly arranged around the lower part of the stirring shaft 22.

[0038] One or more semi-circular pipes 14 are fixed around the outer circumference of the support frame I2. Each semi-circular pipe 14 is connected to the inlet pipe 15 of the air flotation water C. The other end of the inlet pipe 15 is connected to the outlet pipe of the dissolved air tank II. One or more air flotation water C outlet pipes 16 are evenly fixed along the circumference of the outer wall of the semi-circular pipe 14. The other end of the outlet pipe 16 passes through the outer tank 1 and the inner tank 3 and is fixedly connected to the outer wall of the annular dissolved air water release pipe I17 fixed at the bottom of the inner tank 3. Three sets of outlet holes 18 are evenly distributed along the circumference of the upper surface of the annular dissolved air water release pipe I17. The outlet holes 18 of the middle set are vertically upward, and the outlet holes 18 on both sides are inclined to the sides and form a 45° angle with them.

[0039] When treating the sludge slurry B generated in step (2) of Example 2 using the biological treatment device of Example 3, sludge slurry B is injected into the inner tank 3 through the feed pipe 9, and then air flotation water C containing biological bacteria is injected into the inner tank 3 through the liquid inlet pipe 15. After the sludge and water reach the set ratio, the stirring motor 21 is started and the stirring shaft 22 rotates so that the oily sludge and dissolved air water can be fully mixed. After standing, the oil, water and sludge are separated, and when standing, the annular dissolved air water release pipe 17 is located above the sludge-water interface. At this time, the air compressor is turned on to pressurize the dissolved air water to 0.2~0.44Mpa. After the pressure and water level reach the predetermined requirements, the oil on the upper layer of the inner tank 3 is blown onto the annular support plate 6 by the air blowing pipe 10. Pressurized air flotation water is continuously injected while blowing. Then, it flows out from the overflow pipe 8 for collection, while the sewage overflows from the overflow pipe II 11. Stir once after a certain interval, and repeat the above process; after the treatment is completed, drain the water in the middle layer through the drain pipe I12, and discharge the mud C at the bottom layer through the slag discharge pipe 4 for collection.

[0040] The oily sludge processed by this device needs to be pretreated before injection to ensure that the particle size is no larger than 3mm. This is to ensure that it will not block the annular dissolved air water release pipe. Even if a small amount of mud enters the pipe during processing, it will be dispersed when pressurized dissolved air water is introduced, without affecting its use.

[0041] To ensure the ambient temperature during processing, hot water is injected into the annular cavity 5 through the circulating water inlet pipe 19, and the hot water circulates within the annular cavity 5 through the circulating water outlet pipe 20, so as to ensure that the temperature inside the inner tank 3 remains constant.

Claims

1. A biological treatment method for oily sludge, comprising the following steps: (1) Fluidization and screening of oily sludge: Add hot water A at 50-75℃ to oily sludge A, stir to make the sludge easy to flow, and remove plastic products and sand with a particle size greater than 3mm from the oily sludge; (2) Hot washing of oily sludge: Add 50-75°C air flotation water B to the oily sludge-water mixture obtained in step (1), and the weight ratio of oily sludge A: (hot water A + air flotation water B) is 1: (2-5). Stir at a speed of 60-220 r / min for 1-5 minutes, let stand for 10-15 minutes, and then collect the surface crude oil components through an air flotation device. Repeat the above process 12-18 times every 20-30 minutes, and discharge the sewage to the sewage collection tank and sludge slurry B for later use. (3) Biological treatment of oily sludge: The sludge slurry B after hot washing in step (2) is injected into the flotation water C. The weight ratio of sludge slurry B to the injected flotation water C is 1: (1~5). The sludge slurry B is heated and the temperature is maintained at 36~40℃. The pH is adjusted to 6~11. The stirring speed is controlled at 120~220r / min. Saturated aeration is performed. The flotation demulsification is performed once every 8~12 hours. The upper crude oil component C is collected through the flotation device, the middle sewage C is discharged to the sewage collection tank, and the bottom is sludge C. After 4~7 days, the concentration of petroleum hydrocarbons in sludge C drops to below 0.3%, and the treatment of oily sludge is completed. The air-flotated water C is dissolved air water containing microbial fermentation broth, and the effective components of the microbial fermentation broth in the dissolved air water account for 0.1% to 10% by weight. in, In step (3), the microbial fermentation agent is *Rhodococcus flavonoides* (Fan Qingsheng). Rhodococcus qingshengii ), microbacterium leaflets ( Microbacterium foliorum ), Pseudomonas putida ( Pseudomonas putida ), Microbacterium schrenckii ( Microbacterium schleiferi and Dietzia (Dietzia) Highly efficient petroleum-degrading bacteria composed of bacteria in a volume ratio of 3:3:3:3:3; In steps (2) and (3), the injection pressure of the air flotation water is 0.2 to 0.44 MPa.

2. The biological treatment method for oily sludge as described in claim 1, characterized in that... In step (3), waste hydrochloric acid or calcium oxide is added to adjust the pH value.

3. The treatment apparatus for the biological treatment method of oily sludge according to claim 1, comprising a biological tank, characterized in that... The biological tank includes an outer tank (1) and a support frame I (2). The bottom of the outer tank (1) is provided with a through hole. The inner tank (3) is placed inside the outer tank (1) and its bottom is fixed on the through hole. A sludge discharge pipe (4) for mud C is provided at the bottom of the inner tank (3). An annular cavity I (5) is formed between the outer wall of the inner tank (3) and the inner wall of the outer tank (1). A circular annular support plate (6) is fixed between the upper end of the outer wall of the inner tank (3) and the inner wall of the outer tank (1) to seal the annular cavity I (5). The outer tank (1) above the support plate (6) has an overflow pipe I (8) for crude oil component C on one side of the upper part of the outer wall. Above the overflow pipe I (8) is a feed pipe (9) for sludge slurry B. The outer tank (1) has an air blowing pipe I (10) and an overflow pipe II (11) for sewage C in the middle connected to the inner tank (3) on the upper part of the other side of the outer wall. The lower part has an empty pipe I (12) connected to the inner tank (3). The air inlet of the air blowing pipe I (10) is connected to the air tank II pipeline, and the air outlet is placed through the outer tank (1). At the upper edge of the inner tank (3); the upper end of the outer tank (1) is provided with a sealing cover I (13), and a stirring device is provided at the center of the upper end of the sealing cover I (13); one or more semi-circular pipes (14) are fixed around the outer side of the support frame I (2), and the semi-circular pipes (14) are all connected to the inlet pipe (15) of the air flotation water C. The other end of the inlet pipe (15) is connected to the outlet pipe of the dissolved air tank II. One or more air flotations are uniformly fixed along the circumference of the outer wall of the semi-circular pipe (14). The outlet pipe (16) of water C, the other end of the outlet pipe (16) passes through the outer tank (1) and the inner tank (3) and is fixedly connected to the outer wall of the annular dissolved air water release pipe I (17) fixed at the bottom of the inner tank (3); the upper end face of the annular dissolved air water release pipe I (17) has one or more outlet holes (18) evenly distributed along its circumference, and the angle between two adjacent sets of outlet holes (18) is 45°; the annular support plate (6) is inclined from the air blowing pipe I (10) to the overflow pipe I (8).

4. The treatment apparatus for the biological treatment method of oily sludge according to claim 3, characterized in that... The outer tank (1) has a circulating water inlet pipe (19) connected to the annular cavity I (5) on the upper part of one side of its outer wall, and a circulating water outlet pipe (20) connected to the annular cavity I (5) on the lower part of the other side. The circulating water inlet pipe I (19) and the circulating water outlet pipe I (20) are respectively connected to the boiler III pipeline.

5. The treatment apparatus for the biological treatment method of oily sludge according to claim 3, characterized in that... The overflow pipe II (11) is located below the annular support plate (6).

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